The long-term goal of this project is to understand the molecular mechanisms that control inactivation of neuronal Kv4 potassium channels. These potassium channels mediate the transient potassium current that is necessary for coding, integration and amplification of electrical signals in the nervous system. Kv4 channels probably utilize novel mechanisms of inactivation, which are distinct from those better known in Shaker potassium channels. Discoveries made during the last funding period are beginning to shed light on the physiological basis of Kv4 inactivation and how novel subunits shape this process. The specific aims for the next funding period are: (1) To probe conformational changes underlying a prominent pathway of inactivation in Kv4 channels; (2) To map the cytoplasmic moving regions controlling inactivation gating of Kv4 channels; (3) To investigate the molecular mechanisms underlying remodeling of Kv4 inactivation by Kv4-specific neuronal calcium sensors (KChlPs);(4) To investigate the molecular determinants of a KChIP domain with unique modulatory properties. Recombinant DNA technology, patch-clamp electrophysiology and thiol-specific reagents are applied to study inactivation of Kv4 channels expressed in heterologous expression systems (e.g., Xenopus oocytes or mammalian cells). Nuclear magnetic resonance (NMR) is applied to solve the structure of a putative inactivation domain in Kv4 channels. By investigating these aims, this project may gain insights into the molecular basis of brain functions that depend on the precise timing of electrical signaling, a domain where inactivation gating of Kv4 channels plays its most significant role. Specific areas that may benefit from this research include studies of associative learning and epilepsy.